1. Field of the Invention
Embodiments of the present invention relate to indicator devices for cars. The indicator devices convey a driver's intention to drivers of surrounding cars.
2. Description of the Related Art
Japanese Laid-Open Patent Publication No. 2006-298358 and Japanese Laid-Open Patent Publication No. 7-102596 disclose a construction machine. The construction machine has an indicator for indicating a moving direction and the turning direction thereof to people around the same. Japanese Laid-Open Patent Publication No. 2012-67478 discloses an indicator. The indicator indicates the condition of an electric power source switch to the surrounding people. It indicates whether or not an engine is to be started, a condition of a gate lock lever, etc.
There are speed limits under which a car must be operated for safe travel. There are also posted legal speed limits under which cars must travel. It is possible to go beyond such limited speeds as described below. Depending on certain circumstances, a permissible speed for traveling safely may be limited to the limited speed. The circumstances could be a traffic jam, weather-like condition such as rain or fog, a stop sign or signal, the existence of a pedestrian crossing the road, road construction and so on. The limited speed for the car to travel safely under the law will be referred to as a “permissible speed”. The maximum permissible speed will be referred to as a “saturation speed.”
The car may travel at the “saturation speed” for a period of time. When a driver is in a hurry, the driver typically has the intention of maintaining the “saturation speed.” The car may travel at a “non-saturation speed.” For example, when a driver requires safer driving, the driver drives at a speed lower than the “saturation speed.” The car may travel at a “mixed speed.” For example, the “saturation speed” differs from place to place. When the “saturation speed” is high, the car may travel at a “non-saturation speed,” and when the “saturation speed” is low, the car may travel at the “saturation speed.” As a result, even when the “saturation speed” is varied, the driver may sufficiently drive safely. When the car is at rest waiting for a traffic signal to turn green, the “saturation speed” is zero. Thus, even when the car travels while maintaining the “saturation speed,” the speed may become zero. This will be referred to as “heteronomous stop.”
A car may be in a “motionless” state. The “motionless” state includes an “autonomous stop” or a parked state. In the case of “autonomous stop,” the actual speed is zero while the “saturation speed” is not zero.